It is now well recognised that most conventional households as well as commercial premises include a wide variety of electrical products that contain power supplies in order for the appliance to be able to convert the property's mains AC power supply to a usable DC (direct current) to power the relevant electrical appliance or device into operation.
While it may seem a straight forward arrangement for a standard power supply to simply step down the incoming mains AC power supply voltage to a workable DC level, these days however more functionality is required from such devices.
Not only does the power supply technology need to be able to switch from an active mode to a standby mode, it needs to do so with an efficiency so that even in the standby mode when there still is the requirement for the appliance or application to draw some electrical power, that the drawing of this electrical power to supply enough current to devices such as control circuits, micro-controllers and status indicators and so forth in the appliance is done so in an arrangement that meets the requirements now placed by many governments and certification systems demanding not only the simple functionality of having active and standby modes but also the efficiency and the energy savings to operate when each of these modes is selected.
Therefore modern day technology and requirements of a standard power supply system will demand that it provides functionality to present an active mode for the powered device which means that the circuit arrangement allows through the whole of the current necessary for the active circuit, with a minimal voltage drop, and without needless power consumption in this active mode but also in the standby mode the device is also required to be adapted to supply enough current to supply those circuits and controllers still operating in the standby mode of the appliance.
At present there are several methods available including linear regulation, step down transformers and switch mode power supply switches that attempt to provide suitable arrangements in order to establish operable active and standby modes with the required current supply for each mode with the functionality of the electrical appliance to be realised when in use or in standby.
Nonetheless there are problems with conventional linear regulators utilising resistors and/or capacitors. While linear regulators may maintain the desired output voltage by dissipating excess power in ohmic losses, regrettably a linear regulator will just regulate either output voltage or current by dissipating the excess electrical power in the form of heat, and hence its maximum power efficiency in voltage out/voltage in is unacceptable since the volt difference is wasted.
Accordingly these kinds of linear power supplies make them unsuitable in today's environment where emphasis is on saving energy and protecting the environment and so forth by reducing energy consumption.
In order to obtain far greater efficiencies and minimise this wasted energy of linear regulators in the standby mode, sophisticated power supplies that include a semiconductor switcher are now being used. For example a switch mode power supply wherein incorporated into the overall design of the power supply is a switching regulator which is adapted to transfer power from a source-like electrical power grid such as the mains AC power supply to the household appliance while converting voltage and current characteristics. For the most part switch mode power supplies are capable of efficiently providing a regulated output voltage in the standby mode.
Nonetheless any circuit that includes a switching mode power supply at the expense of a more simplified linear power supply introduces complexity into the design which could increase manufacturing costs and so forth, and also as a switch mode power supply operates on the procedure of switching mode supply between full on and full off states by simply varying the ratio of ‘on’ to ‘off’ time of the output signal, this may lead to the generation of high amplitude, high frequency energy, resulting potentially to radio frequency interference (RFI) and/or electro-magnetic interference (EMI), unless expensive and complex filtering is included with the switching circuit arrangement.
Therefore as can be observed from the above conventional methods available for the power supply of adequate current to appliances when they are in either an active mode or standby mode, seems to be lacking in a solution that can not only be simple such as linear regulators in order to provide a current level suitable to operate the device in standby mode but without the losses, but also an arrangement like a switching regulator that provides the high efficiency and energy saving that one would expect from the utilisation of the complicated switch mode power supply arrangements, but without the potential problems associated with RFI, EMI and the complexity of design.
It is therefore an object of this invention to provide a circuit arrangement with a standby mode minimising power and/or current consumption that will be able to provide the necessary current to the device during the standby mode for the device's control circuits, micro controllers, status indicators and so forth to operate in the standby mode, but to operate in this standby mode without simply drawing a linear powered supply, but in fact having a regulated power supply during the standby mode, wherein the regulating activity is not leading to the creation of RFI and EMI problems.